The present invention relates to fuel injection systems for internal combustion engines, in particular, ways of mounting such systems in internal combustion engines.
The modern internal combustion engine is a relatively complex system consisting of many parts. Ever increasing demands for its reliability, smaller overall size, cost reduction on one hand and, on the other hand, the need of performance and emissions improvement, require innovative solutions in order to better meet these, often conflicting, requirements.
The fuel injection system is one of the most sophisticated and expensive systems of the engine, especially in case of diesel engines. A fuel injection system incorporates a great number of components. It also makes a major contribution to the cost of the engine and requires considerable installation space. Some engines have unit injection fuel systems, which are relatively simple installation-wise, because high-pressure fuel pipes are not needed there as high injection pressure is generated and used for the actual injection by one and the same assembly unit. Other engines are equipped with fuel injection systems in which the high fuel pressure necessary for injection is generated remotely from the injectors by a pump, and then high-pressure fuel pipes are utilized for the supply of high-pressure fuel to the injectors.
It is often advantageous for the diesel combustion system to position each injector centrally in the combustion chamber. In order for the overall engine height to be kept to a minimum, it is customary to place injectors entirely under the rocker cover of the engine. In that case, high-pressure fuel pipes have to be brought in from outside of the rocker cover up to the injectors positioned under the cover. The excess pressure and hot oil mist existing under the cover complicate the task of providing a simple, leak-free and easy to assemble/disassemble interface between the pipes and the rocker cover.
One way of dealing with that problem is to arrange the inlet to the space under the rocker cover separately from the cover itself. In the known design solutions, a special area in the cylinder head is allotted for installation of an hydraulic adapter, which effectively provides hydraulic connections on the inside and outside of the rocker cover whilst assuring reliable and durable seal against the oil leakage to the outside of the engine. A drawback of such designs is the relatively large space in the cylinder head that is required for the installation of the adapters. A known way of minimising the space requirement is to use two separate hydraulic adapters, one on the outside and another on the inside of the cylinder head, connected by a channel that is sealed against high fuel pressure at each of the adapters. Still, a considerable space must be reserved on the outside of the cylinder head for installation of the hydraulic adapters, and extra cylinder head material has to be provided for the connecting channel for the fuel. Twice the number of hydraulic adapters in this case also leads to increased costs and complexity.
It is desirable to provide a relatively simple, cost-effective and space-saving means for connecting an injector to a pressure source in an engine.
An aspect of the present invention incorporates a source of fuel pressure positioned outside the space that contains oil-wetted parts of the engine, an injector positioned within said space of the engine, and a fuel pipe for connecting the source of fuel pressure to the injector. The engine also has a component which is positioned outside of the oil-wetted space and is attached to the engine by a screw fastener.
To make hydraulic connection between the source of fuel pressure and the injector, an external fuel pipe is connected between the source of fuel pressure and the fastener, the fastener is made hollow, and an hydraulic adapter is installed inside the oil-wetted space of the engine, said adapter being hydraulically connected to the end of the fastener opposite to its external pipe connection end by means of a drilling made in the engine material. The drilling in the engine is sealed at both the hydraulic adapter end and the fastener end, by well-known means like “O”-ring seals or metal-to-metal sealing connections. The hydraulic adapter is connected to the injector by means of an internal fuel pipe.
An aspect of invention reduces the cost of the engine because no separate hydraulic adapter is required to be installed outside of the oil-wetted space of the engine. Instead, a suitably modified existing fastener of another functional component bolted to the engine, is used for the external hydraulic connection of the fuel injection system. The invention also contributes to reducing the overall size of the engine, because no extra space is required on the outside of the engine for installation of the hydraulic adapters.
Like reference numbers are used to designate corresponding parts of the systems depicted in the drawings.